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Full text of "Text Book Of Mechanical Engineering"

222

Regulator Valve Box.

just scribed vertical line put in contact, both at back and front, with
a line which has been marked on the table. Then set up this line
with square, as shewn, so as to mark the centre of the valve plate,
and measure off to right and left the width of the valve. Scribe
also the thickness of the plate all round. Now set in machine
vice to plane the top surface, as at D, with a front tool, and the
edges with a side tool, and be sure that the travel of the tool is
exactly coincident with the scribed lines. The valve is now re-
moved, and treated similarly for planing at right angles to the
former direction. For this the fork is blocked, as at E, and the
centre squared; next produced upward, as at F, and the width of
valve marked, then planed, as at G. There only now remains the
cutting out of the fork, which is lined by squaring and scribing,
as at H and j; then j is planed out, and H is finished by hand.
Finally scrape the valve surface very truly, as described in a pre-
vious paragraph. It' should be mentioned that when wood is
used to block or bridge a hole, and a centre required, it is ad-
visable to shape a small piece of tin or zinc, as shewn at K, to
receive the compass-point.

VIII. Regulator Valve-box, Cover, and Gland (Fig.
236).—Commence by bridging or 'spanning' the two end holes,
and striking the circle representing the diameter of the flanges, as
shewn at B ; measure also the length of the box over the flanges,
and mark this. The valve-box is now to be mounted on the face
plate of a lathe, and as the casting is "rather long, it must be sup-
ported by angle plates, as shewn at c, being tightly bolted between
them, as well as having one flange fastened to the face plate.
Having been carefully adjusted until central, it is turned on one
flange and surfaced; reversed, and. turned on the opposite flange.
Next place the box on a planing machine, as at D, making sure it
is both level and square, packing if necessary, and having scribed
the top seating and boss, measuring from flange centre, plane
these. Remove, and bolt to slotting machine in a similar manner,
as at E, and slot the front face, measuring the distance a in finish-
ing. It should be noticed that two tools are here, necessary,
cranked respectively to the right and left hand, as at F. Set out*
the bolt-holes in circular flange as at G, and drill with clearance
drill. Set level as at G, and, squaring up the centre line, join this